Yarns composed of multiple filaments are traditionally produced by melt-spinning techniques whereby a melt-spinnable polymer is extruded through relatively small-sized orifices in a spin pack to form a stream of filaments which are substantially immediately solidified in a quench cabinet and converged after solidification to form a yarn composed of multiple filaments. The yarn is thereafter continuously taken up by a high speed winder to form a generally cylindrical yarn package. Depending on the intended end use, the yarn may be flat (undrawn) or may be subjected to a drawing step prior to being taken up to form the package.
In an effort to improve the filament-to-filament cohesion of the yarn so as to ensure that the individual filaments remain integral with the yarn during subsequent processing (e.g., warping), it has been conventional practice to subject the yarn prior to take-up to interlacing. In general, during interlacing, a high velocity fluid (e.g., air, steam or the like) is brought to bear on the converged filaments of the yarn so as to achieve a random mixing or interlacing of the individual filaments comprising the yarn. However, for some high speed spinning operations, fluid jet interlacing is not entirely satisfactory.
According to the present invention, a yarn twister is provided which mechanically twists the yarn prior to take-up so as to improve filament-to-filament cohesion. In this regard, the yarn twister most preferably includes an annular housing defining an annular race in which a follower element is orbitally movable. Pressurized fluid (e.g., air) is introduced substantially tangentially into the race so as to propel the follower in an orbital path along the race. The follower includes a yarn guide element which radially extends through an annular slot in the housing into the housing's interior space. The pressurized fluid is discharged through the slot so as to provide for a fluid bearing for the follower and thereby minimize frictional resistance thereof during its orbital movement. The traveling yarn will thereby be guided through the yarn guide in use so that orbital movement of the follower will responsively impart a desirable twist to the yarn so as to increase the filament-to-filament cohesion of the yarn.
These and further aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiment thereof.